U.S. patent application number 13/447748 was filed with the patent office on 2013-10-17 for method and apparatus of delivering upstream data in ethernet passive optical network over coaxial network.
This patent application is currently assigned to FUTUREWEI TECHNOLOGIES, INC.. The applicant listed for this patent is Jim Chen, Liming Fang, Kira Zhang. Invention is credited to Jim Chen, Liming Fang, Kira Zhang.
Application Number | 20130272703 13/447748 |
Document ID | / |
Family ID | 49325182 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130272703 |
Kind Code |
A1 |
Fang; Liming ; et
al. |
October 17, 2013 |
Method and Apparatus of Delivering Upstream Data in Ethernet
Passive Optical Network Over Coaxial Network
Abstract
An apparatus for interconnecting a fiber-optic network and a
coax network comprising a coax line terminal (CLT) configured to
couple to an optical line terminal (OLT) at the fiber-optic network
and a plurality of coax network units (CNUs) at the coax network
and to cache data received from the CNUs and forward the cached
data to the OLT upon receiving a message from the OLT that assigns
a transmission cycle for a specified CNU, wherein the CLT forwards
the cached data to the OLT upon receiving the message regardless of
whether the cached data corresponds to the specified CNU.
Inventors: |
Fang; Liming; (Santa Clara,
CA) ; Chen; Jim; (Corona, CA) ; Zhang;
Kira; (Wuhan, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fang; Liming
Chen; Jim
Zhang; Kira |
Santa Clara
Corona
Wuhan |
CA
CA |
US
US
CN |
|
|
Assignee: |
FUTUREWEI TECHNOLOGIES,
INC.
Plano
TX
|
Family ID: |
49325182 |
Appl. No.: |
13/447748 |
Filed: |
April 16, 2012 |
Current U.S.
Class: |
398/58 |
Current CPC
Class: |
H04Q 2011/0086 20130101;
H04Q 11/0067 20130101; H04J 14/08 20130101; H04Q 2011/0064
20130101; H04B 10/2575 20130101; H04Q 11/0071 20130101; H04L 12/00
20130101; H04B 10/27 20130101 |
Class at
Publication: |
398/58 |
International
Class: |
H04B 10/20 20060101
H04B010/20 |
Claims
1. An apparatus for interconnecting a fiber-optic network and a
coax network, comprising: a coax line terminal (CLT) configured to
couple to an optical line terminal (OLT) at the fiber-optic network
and a plurality of coax network units (CNUs) at the coax network
and to cache data received from the CNUs and forward the cached
data to the OLT upon receiving a message from the OLT that assigns
a transmission cycle for a specified CNU, wherein the CLT forwards
the cached data to the OLT upon receiving the message regardless of
whether the cached data corresponds to the specified CNU.
2. The apparatus of claim 1, wherein the CLT is further configured
to assign a plurality of upstream transmission time slots to the
CNUs that are comparable to a plurality of upstream transmission
time windows assigned from the OLT for the same CNUs to achieve
asynchronous upstream transmissions between the fiber-optic network
and the coax network.
3. The apparatus of claim 1, wherein the CLT comprises a plurality
of caches for caching a plurality of different priority data
frames, and wherein the CLT forwards the different priority data
frames from the corresponding caches upon receiving the message
from the OLT based on priority regardless whether the data frames
correspond to the specified CNU in the message.
4. The apparatus of claim 1, wherein the fiber-optic network is an
Ethernet passive optical network (EPON), and wherein the message is
a Gate message that assigns a polling cycle for the specified CNU
based on a Multi-Point Control Protocol (MPCP).
5. The apparatus of claim 4, wherein the Gate message comprises a
Logical Link Identifier (LLID) that indicates the specified CNU,
and wherein the CLT forwards the cached data to the OLT without
matching the LLID to the cached data.
6. The apparatus of claim 4, wherein the CLT is further configured
to map the Gate message to a Map message that assigns a comparable
upstream transmission time window as the Gate message and broadcast
the Map message to the CNUs.
7. The apparatus of claim 6, wherein the CLT assigns one or more
time slots that match the upstream transmission time window to one
or more of the CNUs that are indicated in the Map message using one
or more corresponding LLIDS.
8. The apparatus of claim 1, wherein the CLT is further configured
to use a buffer monitor timer to forward CNU cached data at the CLT
during a polling cycle for the OLT, wherein the CNU cached data is
received at the CLT after receiving the message from the OLT.
9. A network component for interconnecting a fiber-optic network
with a coax network in a passive optical network (PON) over coax
system comprising: a receiver configured to receive data from one
or more coax network units (CNUs) in the coax network and a first
message from an optical line terminal (OLT) of the PON that
indicates a specified CNU; a buffer configured to cache the
received data; a processor configured to map an upstream
transmission time window indicated in the first message according
to a first transmission schedule of the OLT to an upstream
transmission time slot according to a second transmission schedule
of the network component; and a transmitter configured to forward
the cached data in the buffer to the OLT upon receiving the first
message and send a second message that comprises the mapped
upstream transmission time slot to the CNUs.
10. The network component of claim 9, wherein the buffer comprises
a plurality of caches for caching a plurality of different priority
data frames, and wherein the different priority data frames are
forwarded from the corresponding caches upon receiving the first
message from the OLT based on priority regardless whether the data
frames correspond to the specified CNU in the first message.
11. The network component of claim 9, wherein the cached data is
received from a different CNU than the specified CNU.
12. The network component of claim 9, wherein the time slot is
assigned to the specified CNU and is indicated in the second
message using a Logical Link Identifier (LLID) associated with the
specified CNU.
13. The network component of claim 9, wherein the second
transmission schedule of the network component assigns a plurality
of time slots for the CNUs that do not overlap with a plurality of
time windows in the first schedule of the OLT that are assigned to
the same CNUs.
14. The network component of claim 13, wherein the time slots of
the second schedule that are assigned to the CNUs are about equal
to the time windows of the first schedule that are assigned to the
same CNUs.
15. The network component of claim 9 further comprising a buffer
monitor timer configured to determine an amount of wait time after
receiving a first message, wherein the buffer monitor timer is
triggered upon receiving the first message if the buffer is empty
of data from the CNUs.
16. The network component of claim 15, wherein the transmitter is
further configured to forward any data that is cached in the buffer
and received from the CNUs to the OLT after receiving the first
message if the buffer monitor timer expires before receiving a next
first message.
17. A method implemented by an apparatus for interconnecting a
fiber-optic network and a coax network comprising: receiving data
from a coax network unit (CNU) at the coax network; caching the
received data in a local buffer; receiving from an optical line
terminal (OLT) at the fiber-optic network a first message that
assigns an upstream transmission window for a specified CNU based
on a first time schedule of the OLT; and forwarding the cached data
in the buffer to the OLT regardless of whether the specified CNU
matches the CNU corresponding to the cached data.
18. The method of claim 17, wherein the local buffer comprises a
plurality of caches for caching a plurality of different priority
data frames, and wherein the different priority data frames are
forwarded from the corresponding caches upon receiving the first
message from the OLT based on priority regardless whether the data
frames correspond to the specified CNU in the first message.
19. The method of claim 17 further comprising: mapping the upstream
transmission window to a comparable upstream transmission time slot
based on a second time schedule for the coax network; and sending
to the coax network a second message that assigns the upstream
transmission time slot to the specified CNU.
20. The method of claim 17 further comprising: receiving from the
OLT a second message that assigns an upstream transmission window;
starting a buffer monitor timer upon receiving the second message
from the OLT if the local buffer is empty of data from the coax
network; receiving subsequent data from the coax network; caching
the subsequent data from the coax network in the local buffer;
sending a third message to the OLT to request extending the
upstream transmission window; and forwarding the cached subsequent
data to the OLT if the buffer monitor timer expires before
receiving from the OLT a next message that assigns an upstream
transmission window.
21. The method of claim 20, wherein the buffer monitor timer is set
up to expire after about one or about two Multi-Point Control
Protocol (MPCP) polling cycles determined by the OLT.
22. The method of claim 20, wherein the first message, the second
message, and the next message are Ethernet passive optical network
(EPON) MPCP Gate messages, and wherein the third message is an EPON
MPCP Report message.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not applicable.
BACKGROUND
[0004] Coaxial cable networks (also referred to herein as coax
networks) have been widely deployed, e.g., in the past two to three
decades. The coaxial cable can provide Gigabit digital bandwidth
that is typically sufficient for broadband access demand. Although
Time Domain Multiplexing (TDM) Passive Optical Network (PON) based
Fiber-to-the-home (FTTH) systems are emerging, due to the
relatively high cost of such systems, coax networks are still
serving many broadband customers today. To support legacy systems
and save investment cost in new infrastructure, integrating some of
the coaxial cable infrastructure with the PON infrastructure is
desirable, such as connecting coax network components at the home
end to PON components at the distribution network and central
office. Ethernet PON (EPON) is one PON technology that uses
Ethernet protocol and frames for communications and can provide
Gigabit bandwidth. EPON over Coax (EPoC) technologies are being
considered to integrate EPONs and coax networks and hence benefit
from both technologies and infrastructures.
SUMMARY
[0005] In one embodiment, the disclosure includes an apparatus for
interconnecting a fiber-optic network and a coax network comprising
a coax line terminal (CLT) configured to couple to an optical line
terminal (OLT) at the fiber-optic network and a plurality of coax
network units (CNUs) at the coax network and to cache data received
from the CNUs and forward the cached data to the OLT upon receiving
a message from the OLT that assigns a transmission cycle for a
specified CNU, wherein the CLT forwards the cached data to the OLT
upon receiving the message regardless of whether the cached data
corresponds to the specified CNU.
[0006] In another embodiment, the disclosure includes a network
component for interconnecting a fiber-optic network with a coax
network in a PON over coax system comprising a receiver configured
to receive data from one or more CNUs in the coax network and a
first message from OLT of the PON that indicates a specified CNU, a
buffer configured to cache the received data, a processor
configured to map an upstream transmission time window indicated in
the first message according to a first transmission schedule of the
OLT to an upstream transmission time slot according to a second
transmission schedule of the network component, and a transmitter
configured to forward the cached data in the buffer to the OLT upon
receiving the first message and send a second message that
comprises the mapped upstream transmission time slot to the
CNUs.
[0007] In yet another embodiment, the disclosure includes a method
implemented by an apparatus for interconnecting a fiber-optic
network and a coax network comprising receiving data from a CNU at
the coax network, caching the received data in a local buffer,
receiving from an OLT at the fiber-optic network a first message
that assigns an upstream transmission window for a specified CNU
based on a first time schedule of the OLT, and forwarding the
cached data in the buffer to the OLT regardless of whether the
specified CNU matches the CNU corresponding to the cached data.
[0008] These and other features will be more clearly understood
from the following detailed description taken in conjunction with
the accompanying drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] For a more complete understanding of this disclosure,
reference is now made to the following brief description, taken in
connection with the accompanying drawings and detailed description,
wherein like reference numerals represent like parts.
[0010] FIG. 1 is a schematic diagram of an embodiment of an EPoC
system.
[0011] FIG. 2 is a schematic diagram of another embodiment of an
EPoC system.
[0012] FIG. 3 is a schematic diagram of an embodiment of an EPoC
system.
[0013] FIG. 4 is a schematic diagram of an embodiment of an EPoC
upstream transmission scheme.
[0014] FIG. 5 is a schematic diagram of another embodiment of an
EPoC upstream transmission scheme.
[0015] FIG. 6 is a flowchart of an embodiment of an EPoC upstream
transmission method.
[0016] FIG. 7 is a schematic diagram of an embodiment of a network
unit.
[0017] FIG. 8 is a schematic diagram of an embodiment of a
general-purpose computer system.
DETAILED DESCRIPTION
[0018] It should be understood at the outset that although an
illustrative implementation of one or more embodiments are provided
below, the disclosed systems and/or methods may be implemented
using any number of techniques, whether currently known or in
existence. The disclosure should in no way be limited to the
illustrative implementations, drawings, and techniques illustrated
below, including the exemplary designs and implementations
illustrated and described herein, but may be modified within the
scope of the appended claims along with their full scope of
equivalents.
[0019] Multiple Ethernet over Coax (EoC) technologies and standards
that have been used for in-home transmission have also been adapted
to enable outdoor coax access from a PON Optical Network Unit (ONU)
to an EoC Head End, which may be a PON OLT. Examples of such EoC
technologies include Multimedia over Coax Alliance (MoCA), the
International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) G.hn standards, the Home Phoneline
Networking Alliance (HPNA), and Home Plug Audio/Video (A/V).
Outdoor coax access may be enabled using customer premise equipment
(CPE) located at the subscriber home. The OLT may be coupled to one
or more CPEs via a corresponding CNU at the coax network side. The
OLT may communicate with a plurality of CNUs via a CLT that may be
positioned between the PON and the coax network. However, these
technologies may not offer end-to-end Fiber to Coax scheduling for
transferring upstream data from the CNU on the coax network to the
CLT and OLT at the fiber-optic network.
[0020] Using EPON for coax cable access is being proposed by
Multiple System Operators (MSOs) worldwide, where the EPON may be
used for last few hundred meters access for EPoC. EPON is a PON
standard developed by the Institute of Electrical and Electronics
Engineers (IEEE) and specified in IEEE 802.3ah. EPON may provide a
relatively simple and flexible way of using optical fiber for last
mile broadband service. The EPON may comprise an OLT configured to
transmit Ethernet frames at an EPON Media Access Control (MAC)
layer. The OLT may implement a Multi-Point Control Protocol (MPCP)
that performs bandwidth assignment, bandwidth polling,
auto-discovery, and ranging. Ethernet frames may be broadcasted
from the OLT downstream to a plurality of ONUs based on Logical
Link Identifiers (LLIDs) assigned to corresponding ONUs. The LLIDs
may be embedded in the preamble of the transmitted frames.
[0021] Typically in the EPON, upstream bandwidth for the different
ONUs may be assigned by sending Gate messages from the OLT to the
ONUs. The OLT may determine upstream transmission time windows for
the ONUs by sending the ONUs' LLIDs in subsequent Gate messages.
Each Gate may be used to assign a transmission or polling cycle
based on the MPCP. When an ONU receives a Gate message that
comprises the ONU's associated LLID, the ONU may begin transmitting
data upstream to the OLT. Similarly, other ONUs may transmit their
data upstream in turn upon receiving their LLIDs in subsequent Gate
messages from the OLT. The ONUs may also send Report messages to
the OLT to request upstream bandwidth. The Report messages may also
comprise LLIDs that indicate the requesting ONUs. This upstream
bandwidth assignment scheme may also be implemented for EPoC
technology, where the Gate messages may be relayed between the OLT
and the ONUs via an EPoC network.
[0022] Disclosed herein is a system and method for improving
upstream data transmission in an EPoC based system or any other
integrated PON and coax system. The upstream data may be sent from
a coax network to an EPON or other fiber based network (other PON)
that is coupled to the coax network. The system may comprise an OLT
at the EPON (or PON), a CLT positioned between the EPON (or PON)
and the coax network, and one or more CNUs coupled to one or more
customer devices (or CPEs) at the coax network. The CLT may be
configured to receive and cache data from the CNUs. The CLT may
then forward the data in the upstream direction to the OLT upon
receiving a Gate message from the OLT, regardless of whether the
data is from the ONU associated with the LLID in the Gate message
or not. As such, the upstream data from the CNUs may be transmitted
to the OLT without synchronizing upstream data transmission from
the CNUs with the OLT.
[0023] The CLT may be configured to allocate upstream transmission
time slots for the CNUs, which may correspond to assigned time
windows from the OLT that are indicated in the Gate messages. The
amount of data cached for different CNUs may match the
corresponding allocated time slots at the CLT. As such, the OLT may
receive about the same indicated amount of data (or data bandwidth)
per upstream transmission cycle. However, the OLT may not
necessarily receive the upstream data for the CNUs at the CNU's
indicated time windows in the Gate messages. Since this upstream
transmission scheme is asynchronous, the scheme may not require
timing components, which may reduce cost and simplify
transmissions. Further, since the CLT forwards the cached data for
any CNU upstream upon receiving a Gate message from the OLT
regardless of the LLID value in the Gate message, the data
transmission cycles for the CNUs may be reduced.
[0024] FIG. 1 illustrates an embodiment of an EPoC system 100. The
EPoC system 100 may comprise an OLT 110 located at an EPON side, at
least one CNU 130 coupled to a plurality of CPEs 140 at a coax
(subscriber) network side, and a CLT 120 positioned between the OLT
110 and the CNU 130, e.g., at an EPoC between the EPON and the coax
network. The OLT 110 may be coupled via a fiber distribution
network or Optical Distribution Network (ODN) 115 to one or more
CLTs 120, and optionally to one or more ONUs (not shown), of the
EPON. The fiber distribution network or ODN 115 may comprise fiber
optics and an optical splitter 117 that couples the OLT 110 to
multiple CLTs/ONUs, including the CLT 120. The CLT 120 may be
coupled to a plurality of CNUs 130 via coax cables 135 and a cable
splitter 137. Although FIG. 1 shows one CLT 120 and one CNU 130,
the EPoC system 100 may comprise any number of CLTs 120 and
corresponding CNUs 130. The components of the EPoC system 100 may
be arranged as shown in FIG. 1 or any other suitable
arrangement.
[0025] The OLT 110 may be part of the EPON and may be any device
configured to communicate with the CNUs 130 via the CLT 120. The
OLT may communicate with one or more CLTs 120 and optionally with
one or more ONUs (not shown) using optical signals transported via
the fibers of the ODN 115. The OLT 110 may act as an intermediary
between the CNUs 130 and another network (not shown). The OLT 110
may forward data received from the other network to the CNUs 130,
and forward data received from the CNUs 130 onto the other network.
Although the specific configuration of the OLT 110 may vary
depending on the type of PON or EPON, in an embodiment, the OLT 110
may comprise a transmitter and a receiver. When the other network
is using a network protocol that is different from the protocol
used in the EPON, the OLT 110 may comprise a converter that
converts the other network protocol into the EPON protocol. The OLT
converter may also convert the EPON protocol into the other network
protocol.
[0026] The CLT 120 may be any device or component configured to
forward downstream data from the OLT 110 to the corresponding CNUs
130 and forward upstream data from the CNUs 120 to the OLT 110. The
CLT 120 may convert the downstream and upstream data appropriately
to transfer the data between the optical fiber and the coax cable.
The data transferred over the fiber (of the ODN 115) may be
transmitted or received in the form of optical signals, and the
data transferred over the coax cables 135 may be transmitted or
received in the form of electrical signals. The CLT 120 may also
encapsulate or frame the data in the fiber-optic network side and
coax network side differently. The CLT 120 may comprise a storage
medium (e.g., a hard drive or memory) that acts as a cache (or
buffer) for caching upstream data from the CNUs 130 to the OLT 110.
The CLT 120 may dedicate an upstream data cache 125 for the CNUs
130, which may be any suitable portion of the storage medium or
memory.
[0027] The CNUs 130 may be any devices configured to transport data
between the CLT 120 and the corresponding CPEs 140. The CNU 130 may
combine the data from a plurality of corresponding CPEs 140 (e.g.,
at the same home) and send the data upstream to the CLT 120. The
CNU 130 may also receive data from the CLT 120 and distribute the
data downstream to the corresponding CPEs 140. Examples of the CNUs
130 include set top boxes, home (wireless) routers, and modems. The
CPEs 140 may be any wired or wireless communications device or
component that may be used to receive and send data, such as
computer desktops, laptops, tablets, phones, and smartphones. In
other embodiments, the OLT 110, CLT 120, and CNUs 130 described
above may be part of any integrated PON and coax network other than
the EPoC, where the PON may be any PON other than an EPON, such as
a Gigabit PON (GPON) or another type of TDM PONs.
[0028] In the case of upstream data transmissions, the CLT 120 may
cache the data received from any of the CNUs 130 at the upstream
data cache 125 before forwarding the data upstream to the OLT 110.
The CLT 120 may forward the cached data from the upstream data
cache 125 after receiving a Gate message from the OLT 110 without
matching the forwarded data to the LLID in the Gate message. The
cached data may be forwarded upstream regardless of the indicated
LLID from the OLT 110 and may or may not correspond to the CNU 130
associated with the LLID in the Gate message. This may remove the
synchronization of upstream transmissions between the coax network
and the fiber-optic network, which may simplify communications and
reduce cost. Further, since the CNU's upstream data may be
forwarded from the CLT upon receiving any Gate message, the CNU's
cached data may be forwarded before receiving the CNU's intended
Gate message. Thus, the CNU's cached data may be transmitted
upstream with reduced delay, which may reduce the upstream data
transmission cycle for the CNU.
[0029] FIG. 2 illustrates another embodiment of an EPoC system 200.
The EPoC system 200 may comprise an OLT 210 (e.g., at an EPON
side), a CNU 230 (at a coax network side), and a CLT 220 positioned
between the OLT 210 and the CNU 230. The OLT 210, CLT 220, and CNU
230 may be configured similar to the OLT 110, CLT 120, and CNU 130,
respectively. The OLT 210 may be configured to assign an upstream
data transmission time window for each CNU 230 according to the
MPCP. The upstream data may be received by the OLT 210 at an EPON
MAC (or physical) layer. The CLT 220 may comprise a plurality of
upstream data caches 225 for caching upstream data from the CNUs
230, which may have different assigned priority levels. The
upstream data caches 225 may be used for caching different priority
of data frames from the CNUs 230. For instance, the data frames
from the CNUs 230 may comprise MPCP (control) frames that may have
high priority, voice frames that may have medium priority, and
other data frames that may have low priority. The different
priority data frames may be cached in corresponding caches 225,
such as in a MPCP frame cache, a voice frame cache, and a data
frame cache, respectively.
[0030] The OLT 210 may send a Gate message to the CLT 220 to assign
an upstream data transmission time window for one or more CNU 230.
The CLT 220 may process the Gate message to map a corresponding
upstream transmission time slot to one or more CNU 230, which may
include the same or different CNUs 230 than indicated in the Gate
message. The CLT 220 may allocate one or more upstream transmission
time slots to one or more CNUs 230 that may be about equal to the
upstream data transmission time window indicated in the Gate
message. However, the upstream transmission time slot(s) may be
assigned or scheduled differently in time than the time schedule of
the OLT 210. The CLT 220 may send the mapped upstream transmission
time slot(s) to the corresponding CNU(s) 230 using a coax message,
which may be broadcast to the CNUs 230. Any type of suitable
message in the coax network that indicates the mapped upstream
transmission time slot(s) to the CNUs is referred to herein as a
Map message. Hence, for each received Gate message from the OLT, a
coax Map message may be sent to the corresponding CNU(s) 230. The
CNUs 230 may then send the upstream data according to the CNUs'
assigned upstream transmission time slots.
[0031] The CLT 220 may allocate the upstream data transmission time
slots for the different CNUs according to a local time scheduling
of the CLT 220, which may be independent from the OLT's time
scheduling. For example, the upstream data transmission time slots
may be allocated to the CNUs according to the schedule of cached
data at the CLT 220 from the different CNUs 230, where for higher
priority received and cached data may be scheduled first. Thus, the
cached data may be forwarded to the OLT 210 from the higher
priority upstream data caches 225 first, e.g., as long as the
amount of forwarded data matches the assigned time slots. This may
also decouple the scheduling of upstream data transmissions from
the OLT's assigned schedule for upstream data transmissions. As
described above, the upstream data transmission bandwidths from the
OLT 210 may still be preserved, since the time slots assigned by
the CLT 220 may be about equal to the time windows assigned by the
OLT 210.
[0032] FIG. 3 illustrates another embodiment of an EPoC system 300.
The EPoC system 300 may comprise an OLT 310, a CLT 320, and a
plurality of CNUs 330, which may be configured as described above.
The OLT 310 may use the MPCP with dynamic bandwidth allocation
(DBA), to schedule upstream data transmissions for the CNUs 330.
Specifically, the OLT 310 may send a plurality of Gate messages
that indicate a plurality of LLIDs and designated time windows for
the corresponding CNUs 330. The Gate messages may be sent
subsequently from the OLT 310 to the CLT 320 according to the OLT's
determined schedule for upstream data transmissions from the CNUs
330. The MPCP scheduling at the OLT 310 may be implemented with
DBA, where the OLT 310 may reschedule the upstream data
transmissions for the CNUs 330 by resending additional Gate
messages to accommodate to changing fiber-optic network (e.g.,
EPON) conditions, such as changes in available bandwidth, failures,
or traffic congestion.
[0033] Upon receiving each Gate message from the OLT 310, the CLT
320 may also use the MPCP with DBA to schedule upstream data
transmissions for the CNUs 330 based on the designated time windows
in the Gate messages. The CLT 320 may map the time windows for the
CNUs 330 to corresponding time slots to reschedule the upstream
data transmissions for the CNUs 330. Specifically, the CLT 320 may
map each time window for each CNU 330 to a comparable amount of
time slots according to the CLT's determined schedule for upstream
data transmissions from the CNUs 330. The CLT's schedule may be
based on cached data conditions (and optionally other local CLT or
coax network resource conditions), such as the order and amount of
cached data from the different CNUs 330. The CLT 320 may send a
plurality of Map messages that indicate the designated time slots
(and LLIDs) for the corresponding CNUs 330. The Map messages may be
sent from the CLT 320 to the CLTs 320 after or upon receiving the
corresponding Gate messages from the OLT 310. The Map messages may
indicate time slots for the corresponding CNUs 330 that may be
about equal to the indicated time windows in the Gate messages for
the CNUs 330. However, the Map messages may indicate a different
order for upstream transmissions from the CNUs 330 than indicated
in the Gate messages.
[0034] For example, the OLT 310 may send to the CLT 320 subsequent
Gate messages that indicate the LLID values, LLID1, LLID3, and
LLID2, for three corresponding CNUs 330, CNU1, CNU3, and CNU2,
respectively, to schedule upstream data transmissions in that order
according to the OLT' s schedule. Hence, the CLT 320 may transmit
three corresponding subsequent Map messages for CNU1, CNU2, and
CNU3, respectively, to schedule upstream data transmissions in that
modified order according to the CLT's schedule. The CLT 320 may
send one Map message at a time for each received Gate message.
[0035] Each of the CNUs 330 may return upstream data to the CLT 320
according to the designated time slots in the received Map
messages. The CLT 320 may cache the data, e.g., for some time, and
subsequently send the cached data upstream to the OLT 310 upon
receiving a Gate message regardless of the LLID indicated in the
Gate message, as described above. The cached data may be sent
upstream to the OLT 310 in the order the data was received and
cached from the CNUs 330, such as on a first in first out (FIFO)
basis. This order may correspond to the CLT's scheduled and
indicated time slots in previously sent Map messages to the CNUs
330. The CLT 320 may send upstream cached data corresponding to one
Map message at a time upon receiving each Gate message.
[0036] FIG. 4 illustrates an embodiment of an EPoC upstream
transmission scheme 400, which may be implemented in the EPoC
systems described above. The EPoC upstream transmission scheme 400
may be implemented by an OLT 410, a CLT 420, and a plurality of
CNUs 430, which may be configured as described above. Initially,
the OLT 410 may send to the CLT 420 a Gate message that indicates a
LLID for one of the CNUs 430, e.g., LLID3 for CNU3. Upon receiving
the Gate message, the CLT 420 may generate a Map message
corresponding to the Gate message, as described above, and send the
Map message to the same CNU 430, CNU3. The Map message may also
indicate the CNU's LLID, LLID3.
[0037] The CLT 420 may also respond to the Gate message by
forwarding data (e.g., one or more packets) that may be previously
received and cached at the CLT 420, without matching the data to
the LLID (LLID3) in the received Gate message. For instance, the
CLT 420 may forward to the OLT 410 the cached data or packets for
other CNUs 430, CNU1 and CNU2, that are not indicated in the Gate
message. The packets or data forwarded upstream may be previously
assigned corresponding time slots and received by the CLT 420 using
previously sent Map messages to the corresponding CNUs 430 (CNU1
and CNU2). The forwarded packets may comprise the LLIDs of the CNUs
430 to indicate the corresponding CNUs, e.g., LLID1 for CNU1 and
LLID2 for CNU2. This may enable the OLT 410 to distinguish the data
received from different CNUs 430.
[0038] After receiving the Map message from the CLT 420, the
intended CNU 430 (CNU3) may respond by sending an amount or size of
data (e.g., a number of packets) that matches the assigned time
slot indicated in the Map message from the CLT 420. The CLT 420 may
receive the data and cache the data. The received packets may
comprise the sending CNU's LLID, e.g., LLID3 for CNU 3. The CLT 420
may subsequently forward the data for the CNU 430 from the cache
when a subsequent Gate message is received, regardless of whether
the Gate message indicates the CNU's LLID (LLID3) or another LLID
for another CNU 430.
[0039] FIG. 5 illustrates another embodiment of an EPoC upstream
transmission scheme 500, which may be implemented in the EPoC
systems described above. The EPoC upstream transmission scheme 500
may be implemented by an OLT 510, a CLT 520, and a plurality of
CNUs 530, which may be configured as described above. Initially,
the OLT 510 may send to the CLT 520 a Gate message that indicates a
LLID for one of the CNUs 530, e.g., LLID3 for CNU3. Upon receiving
the Gate message, the CLT 520 may generate a Map message
corresponding to the Gate message, as described above, and send the
Map message to the same CNU 530 (CNU3). The Map message may also
indicate the CNU's LLID, LLID3.
[0040] At this point, the CLT's cache may be empty or may not
comprise received data from any of the CNUs 530. Thus, the CLT 520
may not forward any CNU data to the OLT 510 upon receiving the Gate
message. After receiving the Map message from the CLT 520, the
indicated CNU 530 (CNU3) may respond by sending an amount of data
that matches the assigned time slot indicated in the Map message
from the CLT 520. The CLT 520 may receive the data and cache the
data. The received packets may comprise the sending CNU's LLID,
e.g., LLID3 for CNU3. Since, the CLT 520 has received the CNU's
data after some time delay from receiving the Gate message from the
OLT 510, the CLT 520 may not forward the CNU's cached data and
instead wait for another Gate message for a next transmission cycle
to arrive from the OLT 510. An OLT transmission cycle may
correspond to the time window between two transmitted Gate
messages. In this situation, the buffer (or cache) at the CLT 520
that holds such data is referred to herein as a dead frame
buffer.
[0041] To forward the cached data and empty the dead frame buffer
(instead of waiting for a next Gate message for the next cycle),
the CLT 520 may send a Report message to the OLT 510 to request
additional time to forward the cached CNU data. This may be
desirable to avoid the situation of receiving subsequent data from
the CNUs 530 and overloading the buffer at the CLT 520 before
receiving the next Gate message form the OLT 510. The CLT 520 may
comprise a buffer monitor timer 522 that may be started upon
receiving a Gate message. When the timer expires after a determined
buffer wait time, such as equal to one or two polling cycles of the
OLT 510, the CLT 510 may send the Report message to the OLT 510 to
extend the time window for transmitting upstream data (before
exchanging a next Gate message). The CLT 520 may then forward the
cached data to the OLT 510. The CLT 520 may send the Report message
and forward the cached data before receiving the next Gate message
if the buffer monitor timer 522 expires before be the next
transmission cycle. Otherwise, the CLT 510 may wait until receiving
the next Gate message before forwarding the cached data. By
extending the time window and transmitting the cached data in the
dead frame buffer, the scheme 500 may avoid wasting or skipping one
transmission cycle without sending any data to the OLT 510. Thus,
the scheme 500 may improve bandwidth utilization and further reduce
the CNU' s upstream data transmission cycle (in the case of a dead
frame buffer situation).
[0042] FIG. 6 illustrates an embodiment of an EPoC upstream
transmission method 600, which may be implemented in the EPoC
systems and schemes described above. The EPoC upstream transmission
method 600 may be implemented by a CLT that may be coupled to and
in communications with an OLT and one or more CNUs. The CLT, OLT,
and CNUs may be configured as described above. The method 600 may
begin at block 602, where a Gate message may be received from an
OLT. The CLT may receive from the OLT the Gate message that
comprises a LLID indicating a CNU. At block 604, a Map message may
be sent to one or more CNUs. Upon receiving the Gate message form
the OLT, the CLT may map the time window indicated in the gate
message to one or more time slots for one or more CNUs. The time
slot(s) of the Map message and the time window of the Gate message
may correspond to about the same time period. The CLT may send a
Map message to one or more CNUs indicating the mapped time slot and
the LLID for each CNU.
[0043] At block 606, the method 600 may verify whether a data
buffer (for the CLT) is empty. If the condition of block 606 is
true, then the method 600 may proceed to block 614. Otherwise, the
method 600 may proceed to block 608. At block 608, the cached data
(in the buffer) may be forwarded to the OLT. The CLT may forward to
the OLT the cached data in the buffer, which may be packets for one
or more CNUs. At block 610, data may be received from the CNU(s).
The CLT may receive one or more packets from one or more CNUs,
e.g., to which the Map messages were sent. At block 612, the data
may be cached in the buffer. The CLT may cache the received data
until a next Gate message is received. The method 600 may then
return to block 602, where a next Gate message is received.
[0044] At block 614, a buffer monitor timer may be started. The CLT
may start the buffer monitor timer to avoid the dead frame buffer
situation described above (in scheme 500). At block 616, data from
the CNU(s) may be received. The CLT may receive one or more packets
from one or more CNUs, e.g., to which the Map messages were sent.
At block 618, the data may be cached in the buffer. At block 620,
the method 600 may verify whether the buffer monitor timer has
expired. For instance, the buffer monitor timer may be set to one
or two transmission or polling cycles of the OLT. If the condition
of block 620 is true, then the method 600 may proceed to block 622.
Otherwise, the method 600 may return to block 602, where a next
Gate message is received before the buffer monitor timer expires.
At block 622, a Report message may be sent to the OLT. The CLT may
send the Report message to the OLT to extend the time window for
the current transmission or polling cycle and empty the dead frame
buffer before the next polling cycle. At block 624, the cached data
(in the buffer) may be forwarded to the OLT. The method 600 may
then return to block 602, where a next Gate message is
received.
[0045] FIG. 7 illustrates an embodiment of a network unit 700,
which may be any device that transports and processes data through
an EPoC system, such as the EPoC systems 100 and 200. For instance,
the network unit 700 may be located in any of the network
components described above, e.g., at the OLT, CLT, or CNU. The
network unit 700 may comprise one or more ingress ports or units
710 coupled to a receiver (Rx) 712 for receiving signals and
frames/data from other network components. The network unit 700 may
comprise a logic unit 720 to determine which network components to
send the packets to. The logic unit 720 may be implemented using
hardware, software, or both. The network unit 700 may also comprise
one or more egress ports or units 730 coupled to a transmitter (Tx)
732 for transmitting signals and frames/data to the other network
components. The receiver 712, logic unit 720, and transmitter 732
may also implement or support any of the transmission schemes and
methods described above. The components of the network unit 700 may
be arranged as shown in FIG. 7.
[0046] The network components described above may be implemented on
any general-purpose network component, such as a computer or
network component with sufficient processing power, memory
resources, and network throughput capability to handle the
necessary workload placed upon it. FIG. 8 illustrates a typical,
general-purpose network component 800 suitable for implementing one
or more embodiments of the components disclosed herein. The network
component 800 includes a processor 802 (which may be referred to as
a central processor unit or CPU) that is in communication with
memory devices including secondary storage 804, read only memory
(ROM) 806, random access memory (RAM) 808, input/output (I/O)
devices 810, and network connectivity devices 812. The processor
802 may be implemented as one or more CPU chips, or may be part of
one or more application specific integrated circuits (ASICs).
[0047] The secondary storage 804 is typically comprised of one or
more disk drives or tape drives and is used for non-volatile
storage of data and as an over-flow data storage device if RAM 808
is not large enough to hold all working data. Secondary storage 804
may be used to store programs that are loaded into RAM 808 when
such programs are selected for execution. The ROM 806 is used to
store instructions and perhaps data that are read during program
execution. ROM 806 is a non-volatile memory device that typically
has a small memory capacity relative to the larger memory capacity
of secondary storage 804. The RAM 808 is used to store volatile
data and perhaps to store instructions. Access to both ROM 806 and
RAM 808 is typically faster than to secondary storage 804.
[0048] At least one embodiment is disclosed and variations,
combinations, and/or modifications of the embodiment(s) and/or
features of the embodiment(s) made by a person having ordinary
skill in the art are within the scope of the disclosure.
Alternative embodiments that result from combining, integrating,
and/or omitting features of the embodiment(s) are also within the
scope of the disclosure. Where numerical ranges or limitations are
expressly stated, such express ranges or limitations should be
understood to include iterative ranges or limitations of like
magnitude falling within the expressly stated ranges or limitations
(e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater
than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a
numerical range with a lower limit, R.sub.1, and an upper limit,
R.sub.u, is disclosed, any number falling within the range is
specifically disclosed. In particular, the following numbers within
the range are specifically disclosed:
R=R.sub.1+k*(R.sub.u-R.sub.1), wherein k is a variable ranging from
1 percent to 100 percent with a 1 percent increment, i.e., k is 1
percent, 2 percent, 3 percent, 4 percent, 7 percent, . . . , 70
percent, 71 percent, 72 percent, . . . , 97 percent, 96 percent, 97
percent, 98 percent, 99 percent, or 100 percent. Moreover, any
numerical range defined by two R numbers as defined in the above is
also specifically disclosed. Use of the term "optionally" with
respect to any element of a claim means that the element is
required, or alternatively, the element is not required, both
alternatives being within the scope of the claim. Use of broader
terms such as comprises, includes, and having should be understood
to provide support for narrower terms such as consisting of,
consisting essentially of, and comprised substantially of.
Accordingly, the scope of protection is not limited by the
description set out above but is defined by the claims that follow,
that scope including all equivalents of the subject matter of the
claims. Each and every claim is incorporated as further disclosure
into the specification and the claims are embodiment(s) of the
present disclosure. The discussion of a reference in the disclosure
is not an admission that it is prior art, especially any reference
that has a publication date after the priority date of this
application. The disclosure of all patents, patent applications,
and publications cited in the disclosure are hereby incorporated by
reference, to the extent that they provide exemplary, procedural,
or other details supplementary to the disclosure.
[0049] While several embodiments have been provided in the present
disclosure, it should be understood that the disclosed systems and
methods might be embodied in many other specific forms without
departing from the spirit or scope of the present disclosure. The
present examples are to be considered as illustrative and not
restrictive, and the intention is not to be limited to the details
given herein. For example, the various elements or components may
be combined or integrated in another system or certain features may
be omitted, or not implemented.
[0050] In addition, techniques, systems, subsystems, and methods
described and illustrated in the various embodiments as discrete or
separate may be combined or integrated with other systems, modules,
techniques, or methods without departing from the scope of the
present disclosure. Other items shown or discussed as coupled or
directly coupled or communicating with each other may be indirectly
coupled or communicating through some interface, device, or
intermediate component whether electrically, mechanically, or
otherwise. Other examples of changes, substitutions, and
alterations are ascertainable by one skilled in the art and could
be made without departing from the spirit and scope disclosed
herein.
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